## Search found 62 matches

Sun Jan 17, 2021 9:38 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: Week 2 Sapling Hw #2
Replies: 5
Views: 43

### Re: Week 2 Sapling Hw #2

Find the equilibrium value of the conjugate base at equilibrium (which would be the same as the hydronium concentration) and divide it by the initial amount of the acid that's given in the problem. Multiply that against 100 for the percentage. Hope this helps!
Sun Jan 17, 2021 9:35 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Week 1 #5
Replies: 8
Views: 43

### Re: Sapling Week 1 #5

Once you've created two equations that can be combined into the final equation, you take the equilibrium constants of the individual reactions and multiply them against each other (K(combined) = K1 x K2)
Sun Jan 17, 2021 9:33 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Sapling Week 1 #5 Similar Problems
Replies: 1
Views: 9

### Re: Sapling Week 1 #5 Similar Problems

This is covered in 5H.1, Multiples of the Chemical Equation.
Sun Jan 17, 2021 9:29 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Reactants and Products
Replies: 9
Views: 31

### Re: Reactants and Products

In a reaction there's two implicit reactions: the forward reaction and the reverse. Depending on the reactants specified in a question, it determines whether we are analyzing the forward or reverse reaction. Though the reactions are related (one is the inverse of the other), they are both different,...
Sun Jan 17, 2021 9:24 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: ICE table values
Replies: 18
Views: 52

### Re: ICE table values

Mol/L is a good standardized value, but as long as the units are the same across for concentration it probably wouldn't matter if all of the values were in mmol/L or something similar, since Ka or Kb are ratios. The important thing is that all of the units for concentration are the same.
Sat Jan 09, 2021 2:48 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Le Chatelier's Principle
Replies: 4
Views: 21

### Re: Le Chatelier's Principle

I do think this would happen in a real world scenario, but if that isn't mentioned in the problem itself, I think we can assume that for the purposes of the problem it doesn't apply!
Sat Jan 09, 2021 2:45 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 5H.1
Replies: 2
Views: 8

### Re: 5H.1

Adding on, this would mean that in 5H.1, b (where the equation is divided by two) would lead to K^(1/2) and c (where the equation is multiplied by two) would lead to K^(2)! Hope this helps
Sat Jan 09, 2021 2:43 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: very large K
Replies: 6
Views: 22

### Re: very large K

Yes, I think that if K was very large, the products would be strongly favored which means any change in them would be negligible.
Sat Jan 09, 2021 2:41 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.13 textbook problem
Replies: 3
Views: 28

### Re: 5J.13 textbook problem

Hi! So this is kinda unlike our other problems where we did ICE box because they give you the K at the different temperatures, meaning we can just directly compare the different K values at the different temperatures. In this case, you want to find which one is the larger K because that would mean ...
Sat Jan 09, 2021 2:40 pm
Forum: Ideal Gases
Topic: value of R
Replies: 24
Views: 74

### Re: value of R

It depends on the units of the quantities in the problem. For example, one of the R values on the equation sheet uses Torr, while others use atm and bar, which are other units for pressure.
Mon Jan 04, 2021 5:39 pm
Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
Topic: 5J.13 textbook problem
Replies: 3
Views: 28

### 5J.13 textbook problem

I'm having a little trouble figuring out how to set up this problem. Does anyone know how to solve it? A gaseous mixture consisting of 2.23 mmol N2 and 6.69 mmol H2 in a 500.-mL container was heated to 600. K and allowed to reach equilibrium. Will more ammonia be formed if that equilibrium mixture i...
Wed Dec 16, 2020 8:57 pm
Forum: Student Social/Study Group
Topic: Helpful Resources
Replies: 6
Views: 45

### Re: Helpful Resources

I heard that Organic Chem Tutor on youtube has good videos for the topics discussed! Thank you, I'll check that one out! Do you know if it cover topics through the entire 14 series? I think so! The general chemistry playlist on the youtube channel seems to cover most topics I think are going to be ...
Wed Dec 16, 2020 8:55 pm
Forum: Naming
Topic: ONO vs. NO2
Replies: 9
Views: 78

### Re: ONO vs. NO2

ONO just helps us see the structure a little easier! It's the same molecule.
Wed Dec 16, 2020 8:53 pm
Forum: Lewis Structures
Topic: Transition Metals Lewis Structures
Replies: 3
Views: 21

### Re: Transition Metals Lewis Structures

Like everyone else said, I think it depends on the question.
Wed Dec 16, 2020 8:51 pm
Forum: General Science Questions
Topic: final timing
Replies: 24
Views: 109

### Re: final timing

I definitely felt the time pressure. Though I did budget my time strictly and get through the questions with time to spare, there was still so little of it that I felt incredibly stressed while checking my answers.
Wed Dec 16, 2020 8:48 pm
Forum: Student Social/Study Group
Topic: Preparing for 14B
Replies: 6
Views: 48

### Re: Preparing for 14B

I'm not sure of all of the topics we'll be discussing, but based on what he's mentioned every now and then during class and previous knowledge from AP chemistry, I'm going to spend a lot of time reviewing Acid/Bases, Equilibrium and Reaction Kinetics! I'm sure they'll be some Thermochemistry as well.
Wed Dec 16, 2020 8:47 pm
Forum: Student Social/Study Group
Topic: Helpful Resources
Replies: 6
Views: 45

### Re: Helpful Resources

I heard that Organic Chem Tutor on youtube has good videos for the topics discussed!
Sun Dec 06, 2020 6:53 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Sigma and Pi bond rotation
Replies: 4
Views: 42

### Re: Sigma and Pi bond rotation

Yes, I believe that in cases where there is a double or triple bond, the pi bond means that the atom does not rotate.
Sun Dec 06, 2020 5:40 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Textbook 1A.15
Replies: 4
Views: 44

### Re: Textbook 1A.15

Using 102.6nm, you should be able to figure out whether it's in the Balmer or Lyman series, which should tell you n(final). Using that value, you can work backwards and find the initial value.
Sun Dec 06, 2020 5:38 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Memorization for final
Replies: 9
Views: 71

### Re: Memorization for final

I think that if there is a question about the naming of coordination compounds we should know the rules for that, though I'm not sure if it's being tested.
Sun Dec 06, 2020 5:37 pm
Forum: Hybridization
Topic: Hybridization of pi bond?
Replies: 1
Views: 22

### Re: Hybridization of pi bond?

Essentially, a double bond has one pi bond and one sigma bond, and a triple bond has one sigma bond and two pi bonds. So by knowing the types of bonds you can understand how many pi and sigma bonds there are attached to a specific atom. In terms of hybridization, it matters how many bonds are being ...
Sun Dec 06, 2020 5:31 pm
Forum: Trends in The Periodic Table
Topic: Focus 1 Exercise 13
Replies: 3
Views: 30

### Re: Focus 1 Exercise 13

I believe that the reason why it's different for oxygen is because it's the first element in which the electrons are paired in the p-orbitals (nitrogen has 3 unpaired electrons, fluorine has 2 paired 1 unpaired). Because of this, it has a slightly lower ionization energy than nitrogen despite being ...
Sun Dec 06, 2020 5:29 pm
Forum: Student Social/Study Group
Topic: final study
Replies: 42
Views: 159

### Re: final study

I'm planning to go through the textbook problems from past chapters as well as the notes I've taken on the outlines. I'm also going to try and make it to all of the review sessions to make sure I'm focusing on important concepts and familiar with the sorts of problems that might show up on the exam.
Sun Nov 29, 2020 5:02 pm
Forum: Sigma & Pi Bonds
Topic: Sapling Q #16
Replies: 14
Views: 105

### Re: Sapling Q #16

Species with delocalized electrons usually have resonance structures, since there's multiple equally likely structures, the electrons are "delocalized" and spread throughout the multiple structures. They also often have double or triple bonds (which have pi bonds, since double bonds have 1...
Sun Nov 29, 2020 4:59 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: H20 complexes
Replies: 3
Views: 48

### H20 complexes

In Wednesday's lecture, I think there was something said about how if you add NH3 or NaCl to TM cations forming complexes with water, the electron rich species replace the H2O ligands. Could someone explain that a little more?
Sun Nov 29, 2020 4:54 pm
Forum: Dipole Moments
Topic: Tetrahedral Atoms and Dipole Moments
Replies: 7
Views: 46

### Re: Tetrahedral Atoms and Dipole Moments

I think it depends if the dipoles are canceled out.
Sun Nov 29, 2020 4:52 pm
Forum: Hybridization
Topic: Lecture #23
Replies: 13
Views: 115

### Re: Lecture #23

Yes, they are delocalized.
Sun Nov 22, 2020 10:29 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Polar Characteristics of molecule
Replies: 5
Views: 30

### Re: Polar Characteristics of molecule

I don't know if it would be called a dipole moment since that's a phenomenon borne out of a substantial difference in electronegativity, but I think there would be a slight difference in electronegativity present in all bonds that are not diatomic.
Sun Nov 22, 2020 10:26 am
Forum: Determining Molecular Shape (VSEPR)
Topic: VSEPR Model Memorization
Replies: 3
Views: 26

### Re: VSEPR Model Memorization

Given electron geometry, there's no real way since tetrahedral electron geometry could mean four bonded atoms or three bonded atoms and one lone pair (and so on). But if we're given the molecular shape, then it's possible! As far as I have things in my notes so far, linear has a VSEPR formula of AX2...
Sun Nov 22, 2020 10:19 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Tips for memorizing different molecular shapes
Replies: 9
Views: 76

### Re: Tips for memorizing different molecular shapes

The hardest part for me was conceptualizing what each shape looked like (as a result of the combination of bonded electrons + lone pairs) but once you have that down, the things that helped me most were associating each of the shapes with the general electron geometry (i.e. square pyramidal + square...
Sun Nov 22, 2020 10:14 am
Forum: Determining Molecular Shape (VSEPR)
Topic: Repulsion Strength
Replies: 8
Views: 59

### Re: Repulsion Strength

Building on from that, if an atom has more lone pairs, then those lone pairs will push down more on the bonded electrons (resulting in more repulsion strength than an atom with only one lone pair or none).
Sun Nov 15, 2020 8:20 pm
Forum: Polarisability of Anions, The Polarizing Power of Cations
Topic: polarizing power
Replies: 3
Views: 20

### Re: polarizing power

In terms of ranking them, cations have higher polarizing power when they have higher charges (Al3+ has a higher polarizing power than Be2+, which is higher than Li+) and when they are smaller, so polarizing power for cations increases across a period and decreases down a group. Anions have higher po...
Sun Nov 15, 2020 8:13 pm
Forum: Sigma & Pi Bonds
Topic: sigma & pi bonds on midterm [ENDORSED]
Replies: 1
Views: 69

### sigma & pi bonds on midterm[ENDORSED]

Does anyone know if we're going to need to know anything about sigma & pi bonds for the second midterm?
Sun Nov 15, 2020 8:09 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: 3d and 4s orbitals
Replies: 4
Views: 41

### Re: 3d and 4s orbitals

You always put 3d10 before 4s2. When we write out the configuration, 4s2 fills first, but 3d is still written before it (i.e. Fe would be [Ar] 3d6 4s2). The configuration for bromine is probably a typo or mistake of some sort.
Sun Nov 15, 2020 8:05 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Outline 2 Orbital Question
Replies: 4
Views: 60

### Re: Outline 2 Orbital Question

Adding on to Victor said about the values of l and how they correspond to each specific orbital. I also believe Lavelle is referring to, in this case, the shape of each of the 4 orbitals. While I don't think Lavelle would make us memorize all of the shapes of each orbital, I believe that he wants u...
Sat Nov 14, 2020 9:13 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Outline 2 Orbital Question
Replies: 4
Views: 60

### Outline 2 Orbital Question

In outline 2, one of the bullet points says, "Name and explain the relationship of each of the four s-, p- and d-orbitals to the properties of electrons in these states.". I'm a little confused about what it's referring to when it says 'properties of electrons in these states', could someo...
Fri Nov 06, 2020 10:30 pm
Forum: Octet Exceptions
Topic: Phosphorus and d-Orbital
Replies: 7
Views: 66

### Re: Phosphorus and d-Orbital

I think I need to first understand the octet rule, can anyone help with that? The octet rule basically states that all atoms are trying to achieve their "noble gas configuration" through bonding (ex. the elements in period two trying to have a full octet like neon), and a full octet of va...
Fri Nov 06, 2020 10:27 pm
Forum: Photoelectric Effect
Topic: Units for energy
Replies: 11
Views: 125

### Re: Units for energy

1/seconds = 1Hz! 1 Joule = 1 kg x m^2 x s^-2 (or kg x mg^2 / s^2, since that's always been easier for me to conceptualize)
Fri Nov 06, 2020 10:24 pm
Forum: Quantum Numbers and The H-Atom
Topic: order of electron cnfiguration
Replies: 13
Views: 116

### Re: order of electron cnfiguration

As far as I understand it, 3d has a higher energy than 4s when they are both unfilled/empty. When they are filled, this switches, and 3d has a lower energy so it's placed before 4s in the configuration.
Fri Nov 06, 2020 10:22 pm
Forum: Ionic & Covalent Bonds
Topic: Formal Charge Equation
Replies: 10
Views: 52

### Re: Formal Charge Equation

Bonds are shared pairs of electrons between two atoms. In the context of formal charge, we count one of each electron pair, so even though each line represents two electrons, we take only one of the electrons into consideration when calculating the FC.
Fri Nov 06, 2020 10:20 pm
Forum: Student Social/Study Group
Topic: Blind sided by Midterm 1 memorization questions, How to study for memorization questions
Replies: 11
Views: 117

### Re: Blind sided by Midterm 1 memorization questions, How to study for memorization questions

I feel like some of the step-up sessions sometimes covered concepts when trying to explain the computations based off of them which helped me to a certain degree! But what helped me most was taking notes on the lecture and using the outlines provided for the first midterm (1 and part of 2) as a kind...
Fri Nov 06, 2020 10:17 pm
Forum: Resonance Structures
Topic: Stability and Delocalized Electrons
Replies: 3
Views: 25

### Re: Stability and Delocalized Electrons

They are more stable because electron delocalization spreads energy over a larger area instead of keeping it confined to a smaller area.
Sun Nov 01, 2020 6:40 pm
Forum: Student Social/Study Group
Topic: Sappling #27
Replies: 3
Views: 45

### Re: Sappling #27

No, the velocity isn't relevant in that question! It's probably just paired with the uncertainty in velocity for the purpose of the problem.
Sat Oct 31, 2020 9:52 pm
Forum: Ionic & Covalent Bonds
Topic: Homework due date
Replies: 49
Views: 336

### Re: Homework due date

The homework is loosely said to be due at the "end of Week 4", and judging by past precedent, I think it's probably due at 11:59 P.M. on Sunday (since anything later would be the beginning of Week 5).
Tue Oct 27, 2020 11:56 am
Forum: Photoelectric Effect
Topic: UA Workshop: Question 4 part b
Replies: 1
Views: 22

### Re: UA Workshop: Question 4 part b

Essentially, since we know we're looking for the longest wavelength possible, we know that there's likely not any excess kinetic energy, so we set that to zero and solve for the energy of a photon setting that equal to the work function. We can solve for the smallest frequency by dividing the work f...
Mon Oct 26, 2020 9:00 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Inconsistencies in Delta Values
Replies: 4
Views: 53

### Re: Inconsistencies in Delta Values

If the problem gives you +/- [a number, let's say it's 5], then the uncertainty would be twice that, or 10. I believe the answer to 1B.27 is an error in the textbook which shows up on the solution manual errors on the website.
Mon Oct 26, 2020 8:56 pm
Forum: Student Social/Study Group
Topic: Studying Concepts
Replies: 6
Views: 65

### Re: Studying Concepts

Highly recommend watching the modules, because they explain the information really well. In terms of familiarizing yourself and getting over test anxiety, what really helped me get comfortable with the quantum concepts was working through a LOT of problems, both in a guided setting (like a step-up s...
Sun Oct 25, 2020 8:10 am
Forum: *Shrodinger Equation
Topic: Schrodinger on MT
Replies: 7
Views: 84

### Re: Schrodinger on MT

From what I've heard from TAs/UAs/Lecture, Schrodinger on the MT is going to be limited mostly to concepts about how when we square the wavefunction it represents probability density (of finding an electron in that region) and how that corresponds to atomic orbitals.
Sun Oct 25, 2020 8:07 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Textbook Problems 1D
Replies: 2
Views: 56

### Re: Textbook Problems 1D

I don't believe any problems correspond quite to midterm content as most - if not all - involve quantum numbers in some way and those aren't on the exam. 1D.25 doesn't, but it also doesn't seem likely considering I don't think we've delved into subshells in detail yet.
Thu Oct 22, 2020 11:00 am
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic and Molecular Spectroscopy
Replies: 5
Views: 48

### Re: Atomic and Molecular Spectroscopy

Atomic spectroscopy is used for atoms while molecular spectroscopy is used for molecules. I believe we just need to be aware that spectroscopy can be used for different things. Lavelle mentioned it in his lecture, as well as the module, that the experiment was used for hydrogen and the specific dat...
Mon Oct 19, 2020 5:54 pm
Forum: Properties of Electrons
Topic: Electron Wave-Particle Duality
Replies: 10
Views: 98

### Re: Electron Wave-Particle Duality

I don't think that light behaves differently depending on the wavelength (i.e. as a particle vs. a wave). If that was true, most of the electromagnetic spectrum wouldn't exist because light would somehow cease to exist as a wave past a certain frequency? Which doesn't seem likely. As far as I under...
Mon Oct 19, 2020 3:21 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Atomic and Molecular Spectroscopy
Replies: 5
Views: 48

### Atomic and Molecular Spectroscopy

Could somebody explain this topic from the outline for the quantum world? Like specifically, the difference between them and the extent to which we should be aware of that for class or the midterm: With respect to electron transitions that give rise to a UV or visible spectrum: understand the differ...
Sun Oct 18, 2020 4:11 pm
Forum: Einstein Equation
Topic: 1B.6 Practice problem
Replies: 1
Views: 32

### Re: 1B.6 Practice problem

I might be wrong, but considering you've calculated the energy per photons (J/photon) and are given the quantity of photons (1 mole), I think you would multiply the energy per photon against Avogadro's number to calculate the total energy change.
Sun Oct 18, 2020 12:45 am
Forum: Trends in The Periodic Table
Topic: Exceptions to Electronegativity
Replies: 6
Views: 179

### Re: Exceptions to Electronegativity

I think noble gases are the only exception.
Sun Oct 18, 2020 12:43 am
Forum: Properties of Electrons
Topic: Electron Wave-Particle Duality
Replies: 10
Views: 98

### Re: Electron Wave-Particle Duality

I don't think that light behaves differently depending on the wavelength (i.e. as a particle vs. a wave). If that was true, most of the electromagnetic spectrum wouldn't exist because light would somehow cease to exist as a wave past a certain frequency? Which doesn't seem likely. As far as I unders...
Sun Oct 18, 2020 12:34 am
Forum: Properties of Light
Topic: Study Advice
Replies: 50
Views: 295

### Re: Study Advice

I think step-up sessions are best if you're struggling with the material a little, and if you feel confident after doing the textbook problems, you should also check the workshops out! The links are available on the Chem 14A website under Peer Learning Sessions and Step-Up Program
Sun Oct 18, 2020 12:31 am
Forum: Student Social/Study Group
Topic: How are you studying?
Replies: 203
Views: 1284

### Re: How are you studying?

Like everyone has said, I take lecture notes and do the textbook readings, but I also found that the Audio Visual modules are super useful! Also, the Step-Up sessions and Workshop problems are really good if you need any extra practice apart from the textbook problems.
Thu Oct 08, 2020 3:20 pm
Forum: Molarity, Solutions, Dilutions
Topic: A solution of CaCl2 in water forms a mixture that is 41.5% calcium chloride by mass. If the total mass of the mixtur
Replies: 4
Views: 35

### Re: A solution of CaCl2 in water forms a mixture that is 41.5% calcium chloride by mass. If the total mass of the mi

I solved that problem by using the percentage (41.5% in your case) and multiplying it against the total mass to find the mass of calcium chloride in the mixture. Then I subtracted that from the total mass to find the mass of water present in the mixture. Hope this helps!
Thu Oct 08, 2020 3:14 pm
Forum: Administrative Questions and Class Announcements
Topic: All Assignments
Replies: 8
Views: 75

### Re: All Assignments

Nope, I think you have everything! Professor Lavelle also encouraged us to do the Fundamentals problems in the textbook, but those aren't "due" in any formal sense.
Wed Oct 07, 2020 11:03 pm
Forum: SI Units, Unit Conversions
Topic: SI Units
Replies: 13
Views: 125

### Re: SI Units

Adding on from what others have said, I think it would probably be best to use the same units provided in the question, and if those aren't clear, default on SI units!
Wed Oct 07, 2020 11:00 pm
Forum: Student Social/Study Group
Topic: GroupMe Link for Discussion 2C
Replies: 1
Views: 39

### GroupMe Link for Discussion 2C

Is there a GroupMe for Discussion 2C? If there is, could I please have the link? Thanks in advance!
Tue Oct 06, 2020 12:44 pm
Forum: Molarity, Solutions, Dilutions
Topic: Sapling HW Question 5
Replies: 10
Views: 111

### Re: Sapling HW Question 5

Yes, I would re-check your significant figures on this one! Mine were different and I got it right.

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